Mass spectrometry is useful for detecting and measuring a wide variety of metabolites, the presence or amount of which can be indicative of certain conditions or disorders. Thus, mass spectrometry can be used, e.g., to diagnose numerous metabolic disorders associated with altered levels of metabolites. One such metabolic disorder is hereditary tyrosinemia, Type I (HT1), which is caused by a deficiency of fumarylacetoacetate hydrolase (FAH) and is associated with increased levels of tyrosine and succinylacetone. HT1 is a childhood disorder that causes liver failure, painful neurological crises, rickets, and hepatocarcinoma. If untreated, death typically occurs at less than 2 years of age, with some chronic forms allowing survival to 12 years of age. It is now possible to treat HT1 with NTBC (or Nitisinone), if treatment is initiated early in life. Thus, there is a major incentive to identify HT1 affected patients by newborn screening or even prenatal screening.